Fixation of atmospheric nitrogen by means of an electric arc



Patented Feb. 26, 1935 l 1,992,566

FlIXATION or ATMOSPHERIC NITROGEN,

i BYMEANS or AN nLno'raIoalso v Emile Briner, Geneva, and Charles Henri Wakker,

' Conches, Geneva, Switzerland ,.No Drawing. Application November 19, 1932, 'Serial No. 643,522.,111 Switzerland November 1; 2;, 1931 coi im 1204 21) Recent researches have established the importhere are used for the production of the arc'ele'c tant 'part played by electronic action in the protrodes consisting of an alloy of metals of a duction' ofchemical efiectsvbyelectric discharges specific weight of at least 5 with metals from the (see E. Briner and A. Rivier, Holt/(Chimp Acta, first and second group of the periodic system 5 vol. 12, page 881, 1929, in which will be found and of a specific weightbelow 4. Metals'of a "5 bibliography relating to they subject) 'Ithas specific weight of at least 5 are for instance c0p indeed been shownth'at electronstake part in per, nickel, iron, etc. Metals of a: specific weight reactions by icausingactivation of moleculesor below L 4 are alkali metals, (such as sodium, atoms *in the systems traversed by-the-electric lithium, etc.) or alkaline earth metals (such as 10- discharge. This is thecase, for exampleQin the calcium, strontium, etc.). This latter group has 10 formationof oxides ofnitrogen by the action of in fact a very high power of emitting electrons the electricrarc on mixtures" of nitrogen and and. a very low ionization'potential. "For this oxygenu r reason they yieldvery easily electrons whose V This being the easethe chemical effects" pro action determines to a greater or lessextentthe duced by means-of anelectric-discharge should chemical reactions produced by means of the 15 be improved by using-asthe material of' the electric discharge. It has in. fact been found electrodes a substance which easily, yields electhat the use of electrodes in'accordance with. the trons. In particular these substances may be invention leads to very appreciable improve;- those which, like the alkaline earth oxides, have ments in the yield in the fixation of nitrogen in a high thermionic emissive powenthat is to say, the form of oxides by the action of'the arcona 20 which easily give ofielectronsat a raised temmixture of nitrogen and oxygen. Illustrations perature. According tothe relationship estab of theseiimprovements' follow hereinafter; Y

lished by Spanner (Annalen der Physik, vol. :75, i It may here be noted that advantage has page 609, 1924) between the thermionic emissive already been taken of the ease with which elec" power and the electronic structure, these subtrons are emitted by alkali and alkaline earth 2; stances should preferably be compounds of metals in the manufacture of cathodes for wire metals belongingtothe g'roupsofthe alkali and less transmitting apparatus, for luminescent alkaline earth metals. It has indeed been recogtubes in illuminated signs and for sparking plugs nized (compare E." Briner, Boner and Rothen, for internal combustion engines. Concerning Helv. Chil'l'l. Actaj'vol. 9, page 6 34,;1926 and Journ. the application of the electrical discharge to 3 as barium oxide.

Chim. Phys.,*vol. 23, page 788, i926) that the chemical action, which application comes into formation of oxides of nitrogen from a mixture question in the present invention, reference may of nitrogen and oxygen by the action of heat is belmade to Patent 1,266,717, relating to a improvedby the presence of a compound such process. for producing oxides of nitrogen by a f means-of the electric arc. The essential feature 35 It has been proposed by Briner and Rivier toof the process of that specification is the use use substances of this kind as'coatings on elecof aluminium or siliconas the metal for the electrodes for use in making oxides of nitrogen by trode; it is stated that the electrodes may alsomeans of an electric arc. (swissspecification contain alkali or alkaline earth metalsythese No.'l41,0l1 and HelvChimQActa, vol. 12, page. metals giving rise to the formation of oxides 88, 1929.) These authors have shown that, in which promote the formation of bxidesof agreement withtheoreticalpredictions, the apnitrogen."

plication to the electrodes of compounds having The improvement attained by the present ina high capacity for emitting. electrons, such as vention, on the contrary, is due essentially to the compounds (oxides or silicates) of alkali metals use of alkali'or alkaline earth metals, the part 45 or alkaline earth metals, improves'the yield of played by which in chemical reactions produced oxides of nitrogen in the fixation of nitrogen as by the electric discharge is easily explicable on oxide by means of the electric arc. The process, the basis of the considerations hereinbefore rehowever, is open to the objection that the coatferred to.

ings of the active compounds do not adhere sufii- In carrying out the invention the alkali or 50 ciently to the electrodes during the long periods alkaline earth metal may be alloyed with any of operation of the are required in an industrial metal of a specific weight of at least 5, such as process. copper, nickel or iron, which are customarily By the present invention the fixation of nitro-, used as electrodes in electric arc furnaces for gen by means of the electric arc is improved if fixing nitrogen in the form of oxides; in U. S. 55

Patent No. 1,517,727 silver is mentioned as useful.

Further also alloys of these heavy metals, such as chromium-nickel steels, nickel-copper alloys (Monel metal) etc., alloyed with alkali and. alkaline earth metals, may be used. On the other hand more than one alkali or alkaline earth metal may be present in an electrode. It is also not absolutely necessary that in .an electric are both electrodes must consist of the alloy disclosed in this invention, since one such electrode in combination with one of, the hitherto usual electrodes, will already yield a good effect.

Excluded from the metals from which the electrodes are to be produced for thepurpose of the invention are aluminium and siliconv and alloys thereof, since the yields which have been obtained with electrodes made from 'thesemetals' are somewhat low.

The favorable action of the alkaliand alkaline earth metals in the process of the inven tion may be seen from the following results, but we do not limit ourselves to the metal combinations mentionedby way of examples, and it is to be understood that other combinations come within the scope of the invention:-

The action of an arc of milliamperes on air at atmospheric pressure Similar improvements have also been observed in a more powerful apparatus operating with a current of 3 amperes and a power of 2-3 kilowatts instead of 140-mi1liamperes and 80-140 watts as in the preceding table.

The results were as follows:-

7 Percentagetim- Output in Potential provel-n-an Electrode liters per of the are lgnhzatpn hour in volts 0 e ergly m the fixation of nitrogen I Percent Cu 5. 7 l, 070 Cu-Li (1.7% Li) 5. 7 750 78 Cu-Li (3% L1) 5. 7 650 108 It will be seen from the foregoing tables that the improvements attained are very substantial and may amount to nearly per cent.

It must be noted that the improvements cannot be attributed to a variation in the power factor of the are for, as is known, this factor is scarcely affected by substituting the alloy for the pure metal. Y

The diminution in the potential attained by the use of the electrodes used in accordance with the invention has the effect of decreasing the output of energy; consequently the temperature of the gases is lower and the decomposition of the oxides of nitrogen is less, so that there is an improvement in the yield with respect to the consumption of electrical units.

The presence of an alkali or alkaline earth metal in the electrodes substantially increases the stability of the arc.

Finally it has been established that, far from promoting wear of the electrodes, the presence in the electrodes of alkali or alkaline earth metals in the small proportions found to be favorable imparts to them anincreased resistance to wear. For example when a mixture of nitrogen and oxygen is subjected to the action of; an are between electrodes of copper, the electrodes are oxidized to a less extent when they contain calcium than when they consist of pure copper. lt should benoted that the alkali metals and alkaline earth metals whose use is contemplated by the invention are actually available cheaply in commerce.

The. addition of alkali and alkaline earth metals, to the electrodes in accordance with the invention thus manifests itself in (1) an improvement in the utilization of energy in the fixation of the nitrogen as oxides of nitro- (2) an increase in the concentration of the nitrogenous products and (3) a much greater stability of the arc.

The invention thus leads to a marked improvement over the hitherto known processes forthe fixation of nitrogen by means of. the electric arc.

What we claim is:

1. A process for the fixation of atmospheric nitrogen by means of an electric arc, wherein the arc is produced by means of electrodes consisting of an alloy of at least one of the metals selected from the group comprising copper, nickel, iron, silver, with metals selected from the group comprising sodium, lithium, calcium, strontium, barium.

2. A process for the production of oxides of nitrogen from a mixture of nitrogen and oxygen by means of an electric arc, wherein the arc is produced by means of electrodes consisting of an alloy of at least one of the metals selected from the group comprising copper, nickel, iron, silver, with metals selected from the group comprising sodium, lithium, calcium, strontium, barium.

- EMILE BRINER.

CHARLES HENRI WAKKER. 

